In the machine tool industry, machines such as lathes, chucking machines, and the like are available with a significant variety of spindle sizes and capacity. The spindle sizes available depend to some extent upon the manufacturer of the machine as well as the type of work which it is intended to handle. A number of different so called "standard" size spindles are used.
For example, a "5C" is a rather common size collet/spindle for a number of different machines. Another larger spindle is the American National Standard Institute (ANSI) "A2-5" spindle which may be made to accept the larger 16C collets, which in turn accept larger diameter work. Many machine shops like to have the capability of using the larger 16C collets, but also need the smaller 5C collets. Such machine shops may have only an occasional need for the larger capacity of the 16C collets, and may have a larger inventory of 5C collets for work up to 1-1/16 inch round. Thus, the adapter of the present invention permits use of the smaller collets on the larger size spindle machines.
In addition, conventional spindle tooling such as live centers, expanding collets, etc. which have the external configuration of the smaller collet could also be used with the adapter and the smaller size collet.
The prior art reveals an adapter also intended for adapting a smaller collet to a large spindle. U.S. Pat. No. 2,478,195 discloses such an adapter which includes a tapered head portion slideably engaged with a threaded tubular portion. The tubular portion in turn threadedly engages the draw tube of the machine tool on its exterior surface and threadedly receives the smaller diameter on its interior surface. However this prior structure suffers from several disadvantages. Specifically, upon release of the draw tube for releasing the work, there is no positive release of the collet. Instead of pushing the collet out of the head portion, to release the work, the adapter is just as likely to push its head portion out of the spindle while retaining full gripping pressure on the workpiece. In addition, the connection between the head portion and the tubular portion of this adapter is such that significant wear can result between the two pieces which in turn can reduce the accuracy of the machine tool.
Accordingly, it is a primary object of the present invention to provide an improved adapter for adapting a collet of a given size to a larger size machine tool spindle.
Another object of the invention is to provide a collet adapter which is spring biased into the spindle even when the collet is released.
A further object of the invention is to provide a collet adapter of improved construction.
An additional object of the disclosed invention is to provide an adapter cap for preventing shifting of the bushing should the collet become jammed thereon thus providing at all times positive release of the collet from the bushing.
Yet another object of the disclosed invention is to provide an adapter cap having seal means for sealing the cap to the reducer bushing to prevent the entrance of dirt and contaminants into the bushing assembly.
Still a further object of the disclosed invention is to provide an adapter cap which has an aperture sized to accept all sizes of collets.
These and other objects and advantages of this invention will become apparent when considered in light of the following description and claims when taken together with the accompanying drawings.